Connection identifier system and method

ABSTRACT

A method and system are proposed for establishing a requested connection between a source node and a destination node in a telecommunications network. The system and method are described in relation to a 3GPP network, but are applicable to other types of networks. The method includes generating a source application identifier for the connection within the source node, retrieving a source node identifier for the source node and transmitting the source application identifier and the source node identifier to the destination to provide a source connection identifier for the requested connection between the source node and the destination node.

TECHNICAL FIELD

The present invention relates to the management of connections intelecommunications networks, particularly but not exclusively networksoperating according to the 3GPP standards or equivalents or derivativesthereof.

RELATED ART

In telecommunications networks, connections may be established betweencomponents or nodes in the network. Connections may be established, forexample, between two base station (eNodeB) components in the network orbetween an eNodeB and a gateway component in the telecommunicationsnetwork. An example of a gateway component may include an AccessGateway, which may be a Mobility Management Entity (MME) or a SystemArchitecture Evolution (SAE) gateway. Connections may be establishedwhen a new mobile communication device or User Equipment (UE) connectsto an eNodeB, for example when a mobile device is switched on or when amobile device transfers from one eNodeB to a different eNodeB in thenetwork. Similarly, connections may be established when an eNodeBcomponent communicates with a new gateway device in the network.

Before establishing a connection, the source node, for example aneNodeB, generates an application identifier for the connection (eNBS1-AP). The application identifier is unique to the connectionscurrently active within the source node. That is, the source node mayhandle a plurality of connections, each having its own applicationidentifier.

The application identifier is transmitted to the destination node withthe initial connection request message, requesting the establishment ofa connection. In response, the destination node transmits a replymessage to establish the connection. The reply message includes both theapplication identifier (eNB S1-AP) generated by the source node and anapplication identifier generated by the destination node. Theapplication identifier for the destination node may be in the form of aTarget eNodeB identifier (eNB S1-AP) if the destination node is anothereNodeB or an MME identifier (MME S1-AP) if the destination node is anMME. The application identifier generated by the destination node isunique to the connections currently active in the destination node. Thatis, the destination node may handle a plurality of connections, eachhaving its own application identifier.

It has been appreciated that, although the application identifiers areunique within the source and destination nodes that generate theidentifiers, the application identifiers do not necessarily uniquelyidentify the connection at the receiving component. This may beproblematic, for example, if two connection request messages for twonewly-connecting mobile devices are received at an MME from twodifferent eNodeBs where the two connection request messages have bychance been assigned the same eNB S1-AP identifier. A problem may alsoarise if S1-AP Handover Request messages are received at an eNodeB fromtwo different MMEs which have assigned the same MME S1-AP identifier tothe requests. Similarly, a problem may arise if an eNodeB componentreceives X2-AP Handover Request messages from two other eNodeBcomponents which have by chance assigned the same Source XP-APidentifier to the requests. A more detailed description of thesesituations and the associated problems is provided below.

The various acronyms applicable in the telecommunications network willof course be familiar to those skilled in the art, but a glossary isappended for the benefit of lay readers. Although for efficiency ofunderstanding for those of skill in the art the invention will bedescribed in detail in the context of a UTRAN (Evolved UniversalTerrestrial Radio Access Network) system, the principles of theidentifier system can be applied to other systems, e.g. 3G, CDMA (CodeDivision Multiple Access) or other wireless systems in which basestation components, such as eNodeB components, communicate with eachother or with other devices, such as gateway devices, in thetelecommunications network, with the corresponding elements of thesystem changed as required. The present methods and systems may also beimplemented in wireless local area networks (WLANs) or other local orwide area networks (LANs or WANs).

DISCLOSURE OF INVENTION

According to one aspect, the invention provides a method forestablishing a requested connection between a source node and adestination node in a telecommunications network comprising:

generating a source application identifier for the connection within thesource node;

retrieving a source node identifier for the source node; and

transmitting the source application identifier and the source nodeidentifier to the destination node to provide a source connectionidentifier for the requested connection between the source node and thedestination node.

Hence the identifier for the connection between the source node and thedestination node includes both an application identifier and anidentifier of the source node itself. The application identifier mayuniquely identify the connection within the source node. This identifiermay be generated by an application identifier generator, which may beassociated with the application that sets up and manages connectionsfrom the source node. Application identifiers may not be unique acrossdifferent nodes in the network, that is two source nodes establishing aconnection may use the same application identifier in relation to eachof their connections. Adding a further identifier based on the sourcenode itself may differentiate the new connection from other connectionsbeing established by other nodes in the network. The source nodeidentifier may be stored in the source node and retrieved from memory orthe identifier may be generated before being incorporated into thesource connection identifier.

A connection between source and destination nodes in the network mayalso be referred to as a “context” and a connection identifier may bereferred to as a “context identifier”.

In one embodiment, the method may further comprise receiving aconnection reply message, the reply message comprising a destinationconnection identifier, wherein the destination connection identifiercomprises a destination application identifier identifying a connectionwithin the destination node and a destination node identifier.

In some implementations, it may be considered sufficient to provide anidentifier of the source node in the connection request message.

The source node identifier may be unique within the mobiletelecommunications network, for example within a single Public LandMobile Network (PLMN) network, or the source node identifier may beglobally unique. In one embodiment, the source node identifier mayinclude an identifier of at least a portion of the source network (forexample an identifier of the PLMN network in which the source node isoperating) and an identifier of the source node within the at least aportion of the source network (for example an identifier of the sourcenode that is unique within the PLMN network).

It will be clear to one skilled in the art that the methods describedmay be implemented between a number of different types of components ina mobile network and over a variety of different interfaces. However, ina specific embodiment, the source and/or destination nodes may comprisebase stations, for example eNodeB components. The source and/ordestination components may also comprise gateway nodes, such as MMEcomponents. The connection may be established over an S1 or X2 interfacedepending on the source and destination components for the particularconnection.

According to another aspect, the invention provides apparatus comprisinga telecommunications network, the network comprising a plurality ofnodes, wherein a connection may be established between two nodes in thetelecommunications network using a connection request message, thenetwork comprising:

a source node for initiating a connection to a destination node in thetelecommunications network, the source node comprising:

means for generating a source application identifier;

means for storing a source node identifier; and

means for transmitting the source application identifier and the sourcenode identifier to the destination node to provide a source connectionidentifier for the requested connection between the source node and thedestination node,

the network further comprising a destination node comprising:

means for receiving the source application identifier and the sourcenode identifier from the source node to form a source connectionidentifier for the requested connection between the source node and thedestination node;

means for generating a connection reply message; and

means for transmitting the connection reply message to the source nodevia the telecommunications network.

According to another aspect, the invention provides apparatus comprisinga source node for originating a connection to a destination node of atelecommunications network, the source node comprising:

means for generating a source application identifier;

means for storing a source node identifier; and

means for transmitting the source application identifier and the sourcenode identifier to the destination node to provide a source connectionidentifier for the requested connection between the source node and thedestination node.

According to another aspect, the invention provides apparatus comprisinga destination node for terminating a connection from a source node of atelecommunications network, the destination node comprising:

means for receiving a source application identifier and a source nodeidentifier to form a source connection identifier for the requestedconnection between the source node and the destination node;

means for generating a connection reply message; and

means for transmitting the connection reply message to the source node.

According to another aspect, the invention provides a method ofconfiguring a telecommunications network comprising:

defining a range of application identifiers for identifying connectionsin the telecommunications network;

dividing the range of application identifiers into a plurality ofsub-ranges of application identifiers; and

allocating a sub-range of application identifiers to each of a pluralityof nodes in the network;

wherein each sub-range of identifiers is allocated so that each node inthe network has a plurality of application identifiers that is distinctwithin the network.

According to another aspect, the invention provides method ofestablishing a connection between a source node and a destination nodein a telecommunications network, wherein a connection request message isused to establish a connection and wherein the connection requestmessage comprises an application identifier selected from a range ofapplication identifiers used in the network, the method comprising:

storing a sub-range of application identifiers for identifyingconnections in the telecommunications network;

retrieving an application identifier selected from the sub-range ofapplication identifiers;

generating a connection establishment request message incorporating theselected application identifier; and

transmitting the connection establishment request message to thedestination node.

According to a further aspect, the invention provides a method ofestablishing a connection from a source node at a destination node in atelecommunications network comprising:

receiving a connection request message from the source node, theconnection request message including an application identifier selectedfrom a range of application identifiers used in the network;

storing a source node identifier for identifying a connection in thetelecommunications network;

generating a connection establishment reply message incorporating theselected application identifier; and

transmitting the connection establishment reply message to the sourcenode.

Preferred embodiments of the method may include defining a networkidentifier for the telecommunications network, wherein the connectionestablishment request message further comprises the network identifier.

The method may further include monitoring which application identifiershave been used for previously-established connections and avoiding usingthose application identifiers for establishing new connections,particularly if the previously-established connections are still activein the node. Application identifiers may be selected by cycling througha list of available application identifiers or by selecting anyidentifier that is not currently in use for a connection.

According to a further aspect, there is provided a method forestablishing a connection between a source node and a destination nodein a telecommunications network by transmitting a connection requestmessage, the message having a source application identifier for theconnection within the source node; and

wherein the message further comprises a source node identifier for thesource node.

According to a further aspect, there is provided a system forestablishing a connection between a source node and a destination nodein a telecommunications network by transmitting a connection requestmessage, the message having a source application identifier for theconnection within the source node; and

wherein the message further comprises a source node identifier for thesource node.

According to a further aspect, there is provided a method forestablishing a connection at a destination node from a source node in atelecommunications network by receiving a connection request message,the message having a source application identifier for the connectionwithin the source node; and

wherein the message further comprises a source node identifier for thesource node.

According to a further aspect, there is provided a system forestablishing a connection at a destination node from a source node in atelecommunications network by receiving a connection request message,the message having a source application identifier for the connectionwithin the source node; and

wherein the message further comprises a source node identifier for thesource node.

The above two aspects may further include receiving a second connectionrequest message from a second source node, the message having a secondsource application identifier; and wherein the second message furthercomprises a source node identifier for the second source node, thesource node identifier for the source node and the second source nodeidentifier for the second source node being mutually distinct.

In one embodiment of the above two aspects, the source node and thesecond source node each comprise an eNodeB and the destination nodecomprises an MME.

In a second embodiment of the above two aspects, the source node and thesecond source node each comprise an MME and the destination nodecomprises an eNodeB.

In a third embodiment of the above two aspects, the source node, thesecond source node and the destination node each comprise an eNodeB.

Aspects of the invention are set out in the independent claims.Preferred features of the aspects are set out in the dependent claims.The invention provides, for all methods disclosed, correspondingcomputer programs or computer program products for execution oncorresponding equipment, the equipment itself (user equipment, nodes,networks or components thereof) and methods of configuring and updatingthe equipment. Features of one aspect may be applied to other aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described, by way of example,with reference to the accompanying drawings in which:

FIG. 1 schematically illustrates a mobile telecommunication system of atype to which the embodiment is applicable;

FIG. 2 schematically illustrates a base station forming part of thesystem shown in FIG. 1;

FIG. 3 schematically illustrates a gateway device forming part of thesystem shown in FIG. 1;

FIG. 4 a schematically illustrates the establishment of a connectionbetween an eNodeB and an MME component;

FIG. 4 b schematically illustrates the establishment of a connectionbetween two eNodeBs;

FIG. 5 schematically illustrates a potential error situation that mayarise in a prior art system;

FIG. 6 schematically illustrates a second potential error situation thatmay arise in a prior art system;

FIG. 7 schematically illustrates a third potential error situation thatmay arise in a prior art system;

FIG. 8 a is a schematic illustration of a first message from an eNodeBto an MME according to one embodiment; and

FIG. 8 b is a schematic illustration of a first message from an MME toan eNodeB according to one embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Overview

The following description sets out a number of specific embodiments ofthe method and system claimed herein. It will be clear to one skilled inthe art that variations of the features and method steps may be providedand that many of the features described are not essential to theinvention, the scope of which is defined by the claims.

FIG. 1 schematically illustrates a mobile (cellular) telecommunicationsystem 1 in which users of mobile (or cellular) telephones (MT) 3-0,3-1, and 3-2 can communicate with other users (not shown) via one of thebase stations 5-1 or 5-2 and a telephone network 7. The telephonenetwork 7 includes a plurality of components including gatewaycomponents 9-1, 9-2. It will be appreciated by the skilled person thatthe each base station 5-1, 5-2 may connect to the telephone network 7via either gateway 9-1, 9-2 and that both base stations 5-1, 5-2 mayconnect via the same gateway 9-1, 9-2. Similarly, each mobile telephone3 may connect to the telephone network 7 via either base station 5 andthat both mobile telephones 3 may connect via the same base station 5.

In this embodiment, the base stations 5 use an orthogonal frequencydivision multiple access (OFDMA) technique in which the data to betransmitted to the mobile telephones 3 is modulated onto a plurality ofsub-carriers. Other well known data transmission techniques may also beused. When a mobile telephone 3 enters the network 7, for example bybeing switched on, a connection is established between the mobiletelephone 3 and a base station 5 and between the base station 5 and agateway device 9. This enables communication between the mobiletelephone 3 and other components in the network 7.

Also, when a mobile telephone 3 moves from the cell of a source basestation (e.g. base station 5-1) to a target base station (e.g. basestation 5-2), a handover procedure (protocol) is carried out in thesource and target base stations 5 and in the mobile telephone 3, tocontrol the handover process. The handover is enabled by theestablishment of a connection between the source and target basestations 5. As part of the handover process, the gateway device 9-1, 9-2via which communications from a mobile telephone 3 are transmitted tothe telephone network may change. Alternatively, the gateway device 9-1,9-2 through which communications are transmitted may remain the same,but the base station 5-1, 5-2 to which the mobile device is connectionmay change. These transfers are also enabled by the establishment ofconnections between the base stations 5 and the gateways 9.

Base Station

FIG. 2 is a block diagram illustrating the main components of each ofthe base stations 5 used in this embodiment. As shown, each base station5 includes a transceiver circuit 21 which is operable to transmitsignals to and to receive signals from the mobile telephones 3 via oneor more antennae 23 and which is operable to transmit signals to and toreceive signals from the telephone network 7 via a network interface 25.The network interface 25 includes an S1 network interface forcommunicating with network components, such as gateway nodes, using theS1 protocol. The network interface 25 also includes an X2 interface forcommunicating with other base station components using the X2 protocol.A controller 27 controls the operation of the transceiver circuit 21 inaccordance with software stored in memory 29. The software includes,among other things, an operating system 31, an application identifiergenerator 33 and a connection identifier generator 35 which may also bereferred to as a context identifier generator. The memory stores a nodeidentifier 34 and in some embodiments also stores a network identifierfor the network with which the base station is associated. The operationof the application identifier generator 33 and the connection identifiergenerator 35 are described below.

Gateway

FIG. 3 is a block diagram illustrating the main components of each ofthe gateway components 9 used in this embodiment. As shown, each gateway9 includes a transceiver circuit 41, which is operable to transmitsignals to and to receive signals from at least one base station 5 via abase station interface 43 and which is operable to transmit signals toand receive signals from the rest of the telephone network 7 via anetwork interface 45. A controller 47 controls the operation of thetransceiver circuit 41 in accordance with software stored in memory 49.The software includes, among other things, an operating system 51, anapplication identifier generator 53 and a connection identifiergenerator 55, which may also be referred to as a context identifiergenerator. The memory stores a node identifier 54 and in someembodiments also stores a network identifier for the network with whichthe base station is associated. The operation of the applicationidentifier generator 53 and the connection identifier generator 55 aredescribed below.

In the above description, both the base stations 5 and the gateways 9are described for ease of understanding as having respective discretemodules which operate according to the methods described herein. Whilstthe features may be provided in this way for certain applications, forexample where an existing system has been modified to implement theinvention, in other applications, for example in systems designed withthe inventive features in mind from the outset, these features may bebuilt into the overall operating system or code and so the modulesdescribed above may not be discernable as discrete entities.

The following description will use the nomenclature used in the LongTerm Evolution (LTE) of UTRAN. Therefore, the mobile telephone 3 will bereferred to as a UE, each base station 5 will be referred to as aneNodeB (or eNB) and each gateway component will be referred to as anMME. The protocol entities used in LTE have the same names as those usedin UMTS (Universal Mobile Telecommunication System) except for the RadioLink Control (RLC) entities which, under LTE, are called the Outer ARQ(Automatic Repeat Request) entities. The Outer ARQ entities of LTE havesubstantially the same (although not identical) functionality to the RLCentities of UMTS.

Error Scenarios

As set out above, in prior art systems application identifiers sent withthe context establishment request messages do not necessarily uniquelyidentify the context at the receiving component. Details of identifiersthat are sent within context set-up messages in this embodiment areprovided below. However, examples of situations in which a problem mayarise are first discussed in more detail.

A transport protocol connection, such as a Stream Control TransmissionProtocol (SCTP) connection, may carry signals relating to different UEs.In order to forward the signalling internally to the correct UE contextmanager in the receiving node, application routing information isincluded in the S1 or X2 application (AP) messages. This will be furtherexplained and illustrated with reference to FIGS. 4 a and 4 b.

When a sending node requests, in some cases implicitly, theestablishment of a dedicated S1/X2 signalling connection for a certainUE, e.g. by sending an S1-AP Initial UE message, it informs the peernode on the S1/X2 interface the application (AP) identifier it hasassigned for that UE. In the case of a connection between an eNodeB 61and an MME 63, this message takes the form “eNB S1-AP” 65 as shown inFIG. 4 a, which may also be written as “eNB S1-AP UE ID”. For a transferfrom one eNodeB 69 to a peer eNodeB 71, the message is of the form“Source eNB S1-AP” 73 as shown in FIG. 4 b. The response message of thepeer node then contains the S1/X2 Application Identifier of both theoriginating and the peer node, for example “eNB S1-AP, MME S1-AP” 67 asin FIG. 4 a, which may also be written as “eNB S1-AP UE ID, MME S1-AP UEID” or, in the case shown in FIG. 4 b “Source eNB S1-AP, Target eNBS1-AP” 75.

Further details of the application identifiers used in the S1 and X2interfaces are provided below:

eNodeB S1-AP UE Identity

The eNodeB S1-AP UE Identity 65 is allocated to uniquely identify the UEover the S1 interface within the eNodeB 61. When an MME 63 receives theeNodeB S1-AP UE Identity 65, it stores it for the duration of theUE-associated logical S1 connection for this UE. Once known to the MME63, this Identity (IE) may be included in all UE associated S1-APsignalling (uplink (UL) as well as downlink (DL)).

MME S1-AP UE Identity

The MME S1-AP UE Identity 67 is allocated to uniquely identify the UEover the S1 interface within the MME 63. When the eNodeB 61 receives theMME S1-AP UE Identity it stores it for the duration of the UE-associatedlogical S1 connection for this UE. Once known to the eNodeB, 61 the IEmay be included in all UE associated S1-AP signalling (UL as well asDL).

Source eNodeB UE Context ID

The source eNodeB UE Context ID (Source eNB S1-AP) 73 is allocated touniquely identify the UE over the X2 interface with the source eNodeB69. When the target eNodeB 71 receives the source eNodeB context ID, itstores it for the duration of the context for that UE. Once known to thetarget eNodeB 71, the IE may be included in all UE associated X2-APsignalling.

Target eNodeB UE Context ID

The target eNodeB UE Context ID (Target eNB S1-AP) 75 is allocated touniquely identify the UE over the X2 interface with the target eNodeB71. When the source eNodeB 69 receives the target eNodeB context ID, itstores it for the duration of the context for that UE. Once known to thesource eNodeB 69, the IE may be included in all UE associated X2-APsignalling.

Hence, as set out above, in previous embodiments, the ApplicationIdentifiers (AP IDs) are unique within the generating node. As aconsequence, they may not be uniquely identified at the receiving peernode when it receives the first message (i.e. before the signallingconnection exists). There are described below some scenarios depictingpotential error situations in cases in which the application identifieris not unique in the receiving node.

In some situations, errors occur due to a node receiving two messagesfor triggering the establishment of an S1 or X2 connection containingthe same S1/X2 application identifier from the originating node.

A first error situation will be described with reference to FIG. 5. InFIG. 5, two eNodeBs 77, 79 are connected to the same MME 81. The MME 81receives two S1-AP Initial UE messages, which should trigger theestablishment of two S1 connections. However, the two eNodeBs 77, 79have by chance assigned the same eNB S1-AP UE identity to the messages.The application layer in the MME 81 produces an error since it cannotmake a distinction between the two messages. Error handling is thenundertaken by the system, which may result in a delay in connectionsbeing established or a failure to establish at least one connection.

A second potential error situation is illustrated in FIG. 6, whichillustrates schematically a flex scenario. The eNodeB 83 is the targetfor both UE1 89 and UE2 91, served respectively by MME1 85 and MME2 87,during an intra LTE Handover with MME involvement. During the Handoverprocess, the MME 85 sends to the target eNodeB 83 the S1-AP HandoverRequest message. The target eNodeB 83 may receive two S1-AP HandoverRequest messages from the two MMEs 85, 87 containing the same MME S1-APUE Identity. The application layer in the target eNodeB 83 produces anderror since it cannot make a distinction between the two messages. Errorhandling is then performed, which may cause delays and communicationproblems as above.

A further problem in the situation illustrated in FIG. 6 arises if an S1Handover Cancel message is sent before the S1 Handover RequestAcknowledgement is received. In this situation, the target eNodeB 83will not know which resources to release.

A third potential error situation is illustrated in FIG. 7 whichillustrates intra LTE mobility without MME involvement. In thissituation, eNodeB2 99 is the target eNodeB for an intra LTE Handovertriggered by eNodeB1 97 for an intra LTE Handover triggered by eNodeB393. As a consequence, eNodeB2 99 receives two X2 Handover Requestmessages from eNodeB1 97 and eNodeB3 93 which by chance use the sameSource eNodeB UE Context ID. The application layer in the target eNodeB299 may get confused and cannot make a distinction between the twomessages. Error handling is then performed to resolve the situation.

A further problem in the situation illustrated in FIG. 7 also arises ifa Handover Cancel Request is received from eNodeB1 97 or eNodeB3 93before eNodeB2 99 can reply to the original Handover Request. In thiscase, the eNodeB2 99 will not know which resources should be released.

Operation

To avoid situations such as those set out above, it has been appreciatedthat further identification of connection request messages would behelpful. This is implemented by enabling the S1 and X2 interfaces to usedistinct application identifiers. This may be achieved in a number ofdifferent ways and these are summarised and described in more detailbelow.

In one embodiment, a new Node Identifier is added to the relevantS1/X2-AP messages. The Node Identifier may identify the source eNodeB orMME. In this embodiment, the Node Identifier is used only in the firstmessage, in which the connection establishment is requested. The NodeIdentifier is not needed for the reply message and subsequent messages,which revert to exchanging only the application identifier. This reducesthe amount of information (bits) that needs to be carried in thesubsequent messages. This implementation is illustrated schematically inFIGS. 8 a and 8 b. FIG. 8 a illustrates a first message from an eNodeBto an MME which includes both an eNB S1-AP UE id and an eNB Global id.FIG. 8 b illustrates a first message from an MME to an eNodeB whichincludes both an MME S1-AP UE id and an MME Global id. Hence apredetermined number of bits are reserved in the initial S1-AP messageto represent an identifier for the eNodeB or MME.

In an alternative embodiment, a Node Identifier is embedded inside theeNB/MME S1-AP identifier IE. That is, the connection request messageincludes a single identifier, but the identifier incorporates bothinformation sufficient to identify the source node and information toidentify the connection within the source node.

In a further embodiment, a new IE is added representing a logicalidentifier that is related by means of a well known function to atransport layer (TNL) identifier for the node, such as the IP address orSCTP port for the node. For example each eNodeB will have a different IPaddress and this may be used to derive a source node identifier. It isfurther noted that, in a typical implementation, the TNL does not informthe application protocol of the source IP address, thus the applicationprotocol is agnostic of the sender ID unless it is indicated in theapplication message itself. This arises from the UMTS concept that theTNL and RNL should be implemented independently.

In a further implementation, the range of S1/X2-AP identifiers that oneeNodeB or MME can assign is restricted so that the identifier ranges fortwo nodes do not overlap. This may be done, for example, by configuringa different range of identifiers for each eNodeB or MME during thepre-operational stage. Each node then cycles through its predefinedrange of identifiers as it establishes connections. This solutionenables a unique application identifier to be provided from each nodewithin one network. A further network identifier (such as the PLMN ID)may also be needed in some implementations where multiple networks areused to identify the network. This may be provided either embedded inthe application identifier or as a separate identifier.

The implementation of a system according to any of the embodimentsdescribed above resolves the error situations set out above.

In the first error situation that was illustrated in FIG. 5, theaddition or incorporation of an eNodeB identifier into each of the S1-APInitial UE messages from eNodeB1 77 and eNodeB2 79 provides a uniqueidentifier for each connection request received at the MME and henceenables the MME to provide a one-to-one mapping between the eNB S1-AP UEid and the MME S1-AP UE id.

Similarly, in the second error situation described in relation to FIG.6, the addition or incorporation of an MME identifier into each of theMME S1-AP UE identifiers from MME1 85 and MME2 87 would uniquelyidentify the MME messages (and hence the originating MMEs) at the eNodeB83. Further, if the handover request was cancelled, since the MMEs areuniquely identified in the initial message, the eNodeB 83 would knowwhich resources to release to enable a connection to be cancelledwithout affecting establishment of the other connection.

Finally, in the third error situation described in relation to FIG. 7,eNodeB1 and eNodeB3 would send X2-AP Handover Requests including sourceeNodeB identifiers. Hence eNodeB2 could uniquely identify each of thetwo source nodes and would know which resources to release if thehandover request was cancelled.

In one embodiment, in the third situation described in relation to FIG.7, the Handover Request message also contains an MME S1-AP UEidentifier, which includes an identifier of the MME component for the S1signalling connection. This enables the target eNodeB2 99 to contact theMME by looking to the MME S1-AP UE identifier.

The node identifiers incorporated in the connection setup messages maybe globally unique or may be unique only within the telephone network inwhich the node operates, for example within the node's PLMN network. Inone embodiment, a global node identifier may be provided by making useof both a node ID (which is unique within a PLMN) and a PLMN identifier.This would enable each S1/X2 AP to be unique even in a RAN sharingscenario.

The application identifiers for the connection are transmitted with theinitial connection set up messages. To reduce the overhead in subsequentmessages, node identifiers may be omitted from at least some of themessages subsequently sent within the connection.

As mentioned above, the establishment of a connection in a mobiletelecommunications network may occur when a new mobile device (UE)enters the network, for example when the mobile device is switched on.New connections may also be established to enable handover as a mobiledevice moves within a network. Additionally, connections may beestablished due to configuration changes in the network nodes, forexample if a new base station is added or an MME fails.

The generation of an application identifier may be achieved by providinga generator module that uses an algorithm to generate an applicationidentifier dynamically. In an alternative embodiment, the applicationidentifier may be retrieved from a memory or buffer and the node maycycle through using a sequence of different application identifiers forsequential connections.

To determine a node identifier, the node may simply retrieve a fixedidentifier from storage in memory. Alternatively, the node may obtainits identifier from a generator module that dynamically generates a nodeidentifier. As set out above, the node identifier may be based on atransport layer identifier for the node, such as an IP address for thenode.

In one embodiment, the connection identifier is generated using theapplication identifier and the node identifier. In a further embodiment,the connection identifier is generated using the application identifierand the network identifier. In a third embodiment, the connectionidentifier is generated using the application identifier, the nodeidentifier and the network identifier. The identifiers may beconcatenated to form a single connection identifier or a function may beused to combine the identifiers. The use of a function to combine theidentifiers may make the connection identifier shorter than it would beif the identifiers were concatenated. However, concatenation of theidentifiers may enable individual identifiers to be removed fromsubsequent messages once the connection has been established.

GLOSSARY OF 3GPP TERMS

-   LTE—Long Term Evolution (of UTRAN)-   eNodeB—E-UTRAN Node B-   AGW—Access Gateway-   UE—User Equipment—mobile communication device-   DL—downlink—link from base to mobile-   UL—uplink—link from mobile to base-   AM—Acknowledge Mode-   UM—Unacknowledge Mode-   MME—Mobility Management Entity-   UPE—User Plane Entity-   HO—Handover-   RLC—Radio Link Control-   RRC—Radio Resource Control-   RRM—Radio Resource Management-   SDU—Service Data Unit-   PDU—Protocol Data Unit-   NAS—Non Access Stratum-   ROHC—Robust Header Compression-   TA—Tracking Area-   U-plane—User Plane-   TNL—Transport Network Layer-   S1 Interface—Interface between Access Gateway and eNodeB-   X2 Interface—Interface between two eNodeB-   MMEs/SAE Gateway—New name for Access Gateway having both MME and UPE    entities

The following is a detailed description of the way in which the presentinventions may be implemented in the currently proposed 3GPP LTEstandard. Whilst various features are described as being essential ornecessary, this may only be the case for the proposed 3GPP LTE standard,for example due to other requirements imposed by the standard. Thesestatements should not, therefore, be construed as limiting the presentinvention in any way.

Title: Use of Global Node Id in Support of Application Routing

1 SCOPE

The scope of this contribution is to:

-   -   highlight some error scenarios which are caused by the S1/X2        application identifier not being globally unique    -   propose several solutions to overcame this issue

2 DISCUSSION

2.1 Current status

An SCTP connection carries signalling related to different UEs. In orderto forward internally the signalling to the correct UE context manager,application routing information must be included in the S1/X2 APmessages.

Whenever a sending node requests implicitly the establishment of adedicated S1/X2 signalling connection for a certain UE, by e.g. sendingthe S1-AP Initial UE message, it will inform the peer node on the S1/X2AP identifier it has assigned for that UE.

The response message of the peer node will contain, in a normalscenario, the S1/X2 application id of both originating and peer node(see FIGS. 4 a & 4 b).

See below definitions of Application identifier in both S1 and X2interface [1]:

eNB S1-AP UE Identity:

The eNB S1-AP UE Identity shall be allocated so as to uniquely identifythe UE over the S1 interface within the eNB. When MME receives eNB S1-APUE Identity it shall store it for the duration of the UE-associatedlogical S1-connection for this UE. Once known to MME this IE is includedin all UE associated S1-AP signalling (UL as well as DL).

MME S1-AP UE Identity:

The MME S1-AP UE Identity shall be allocated so as to uniquely identifythe UE over the S1 interface within the MME. When eNB receives MME S1-APUE Identity it shall store it for the duration of the UE-associatedlogical S1-connection for this UE. Once known to eNB this IE is includedin all UE associated S1-AP signalling (UL as well as DL).

Source eNB UE Context ID:

The source eNB UE Context ID shall be allocated so as to uniquelyidentify the UE over the X2 interface within the source eNB. When targeteNB receives source eNB UE Context ID it shall store it for the durationof the context for this UE. Once known to target eNB this IE is includedin all UE associated X2-AP signalling.

Target eNB UE Context ID:

The Target eNB UE Context ID shall be allocated so as to uniquelyidentify the UE over the X2 interface within the target eNB. When targeteNB receives target eNB UE Context ID it shall store it for the durationof the context for this UE. Once known to source eNB this IE is includedin all UE associated X2-AP signalling.

The exact definitions are not yet agreed but it is well known/agreedamong the 3GPP groups that these application identifiers are uniquewithin the generating node.

According to the definitions above these AP ids, are unique within thegenerating node. As a consequence they are not univocally identified atthe receiving peer node when it receives the first message (i.e.signalling connection does not exist) unless some node-specificidentifier are also present in the message. In the paragraph 2.3 somescenarios, depicting the potential error situation in case of theapplication id is not globally unique, are explained.

2.2 T-Plane Identifiers

Since Control Plane relies on SCTP over IP on both S1 and X2 interface,following TNL identifiers exist:

SCTP Layer:

-   -   Source Port Number, Destination Port Number    -   SCTP stream id        IP Layer:    -   Source/destination IP address

In LTE there will be one SCTP association for each S1/X2 interface, withone pair of SCTP streams for common procedure and few pairs of SCTPstreams to be shared by all S1/X2 dedicated signalling connections.

The SCTP Source port in combination with the source IP address, the SCTPdestination port and possibly the destination IP address is used toidentify the association to which this packet belongs.

As a consequence, the SCTP association may be used as node identifier(SCTP stream id is not useful for this purpose).

However, in line with the UMTS principle, it is proposed not to use theTNL identifier (i.e. SCTP association) for application protocol purposein order to keep the RNL and TNL as much independent as possible and toavoid any implementation constraints for e.g. blade/SW entitiescommunication.

2.3 Potential Error Situation Scenarios

This paragraph lists some possible scenarios which may lead to an errorsituation in a peer node receiving two messages (which trigger theestablishment of S1/X2 connection) containing the same S1/X2 applicationidentifier the originating node.

-   -   1) In FIG. 5, two eNBs are connected to the same MME: the MME        receives two S1-AP Initial UE messages (which should trigger the        establishment of the S1 connection), from 2 different eNBs which        by chance have assigned the same eNB S1-AP UE Identity.        -   The application layer in the MME will get confused and,            since the message does not contain any information related            to the originating node, it cannot make a distinction            between the two messages. Error handling will then be            performed according to the implementation. This could be            avoided by using an S1-AP identifier which is globally            unique.    -   2) In FIG. 6, an S1 flex scenario is depicted: the eNB is the        target eNB for both UE1 and UE2, served respectively by MME1 and        MME2, during an Intra LTE Handover with the MME involvement.        During the Handover preparation, the MME sends to the target eNB        the S1-AP: Handover Request message. The target eNB may receive        two S1-AP: Handover Request messages from the two different MMEs        containing the same MME S1-AP UE Identity.        -   The application layer in the target eNB will get confused            and, if the message does not contain any information related            to the originating node it cannot make a distinction between            the two messages. Error handling will then be performed            according to the implementation. This could be avoided by            using an S1-AP identifier which is globally unique.    -   3) In FIG. 7, eNode B2 is the target eNB for the Intra LTE        Handover triggered by eNB1 and the Intra LTE Handover triggered        by eNB3. As a consequence the eNB2 may receive two X2: Handover        Request messages from eNB1 and eNB3 which by chance have        assigned the same Source eNB UE Context ID.        -   The application layer in the target eNB2 will get confused            and, since the message does not contain any information            related to the originating node, it cannot make a            distinction between the two messages. Error handling will            then be performed according to the implementation. This            could be avoided by using a Source eNB UE Context ID (i.e.            X2 AP identifier) which is globally unique.            2.4 Proposals

In order to avoid these misleading situations, it is proposed to use aglobally unique application id on both S1 and X2 interfaces. This may bereached in different ways:

Solution One:

-   -   Add a new IE, i.e. Global Node id, in the relevant S1/X2-AP        messages

Solution Two:

-   -   Embedding the Global Node id inside the eNB/MME S1-AP identifier        IE

Solution 3:

-   -   Add a new IE representing a logical identifier which somehow is        related (by mean of a well known function) to TNL identifier (IP        address/SCTP port)

Solution 4:

-   -   Restrict the range of S1/X2AP identifiers that one eNB can        assign so that the range of the two different nodes do not        overlap (by e.g. configuring a different range for each eNB        during the pre-operational state). This solution however will        allow having a unique AP-id within one network. As a consequence        a network identifier (i.e. PLMN id) is needed either embedded in        the AP-id IE or as a separate IE. In case of a separate IE, this        will be needed only in the message triggering the connection        establishment.

Solution one and two rely on the concept of Global node identifier whichmake use of:

Node id (unique within one PLMN) and PLMN identifier (this guaranteethat the S1/X2 AP are unique even in a RAN sharing scenario).

The first three solutions differ in terms of implementation complexity:NEC preference is Solution 1.

In case of solution one, the Global Node id will be needed only for thefirst message. Global Node id is not needed for the reply messageneither for subsequent messages.

Therefore, amount/bits of information that needs to be carried in thesubsequent messages can be reduced by applying solution one.

The fourth solution requires some configuration to be done in the nodesin a pre-operational state.

3 CONCLUSION

This contribution has pointed out some potential error scenarios due tothe S1/X2-AP ids not being globally unique.

Four proposals have been made to overcome this issue i.e.:

-   -   Introduction of Global Node id IE in relevant S1/X2 messages    -   Embedding of the Global node id in the S1-AP id IE    -   Add a new IE representing a logical identifier related to TNL        identifiers    -   S1-AP range configuration in each eNB in combination with a        network identifier (either as a separate IE or embedded in the        AP id IE).

It is proposed to discuss the consequences of not having a uniqueapplication id and to agree on one of the proposals listed in paragraph2.4.

If the principle is accepted, NEC is available in writing the relatedCR.

4 REFERENCE

R3-071344 “Discussion and proposal for the AP ID handling”, NEC

This application is based upon and claims the benefit of priority fromUnited Kingdom Patent Application No. 0715940.3, filed on Aug. 15, 2007,the disclosure of which is incorporated herein in its entirety byreference.

The invention claimed is:
 1. A method, performed by a source nodecomprising a first base station, for establishing a requested connectionbetween the source node and a destination node comprising a second basestation in a cellular telecommunications network, the method comprising:generating a source application layer identifier for the connectionwithin the source node, wherein said source application layer identifieris configured to identify user equipment associated with said sourcenode; retrieving a source node identifier for the source node; andtransmitting, from the source node comprising the first base station,the source application layer identifier and the source node identifierto the destination node comprising the second base station, to provide asource connection identifier for the requested connection between thesource node and the destination node.
 2. A method according to claim 1further comprising: receiving a connection reply message, the replymessage comprising a destination connection identifier, the destinationconnection identifier comprising a destination application layeridentifier for the connection within the destination node and adestination node identifier.
 3. A method according to claim 2, whereinthe destination node identifier is unique within the telecommunicationsnetwork.
 4. A method according to claim 2, wherein the destination nodeidentifier is globally unique.
 5. A method according to claim 2, whereinthe destination node identifier comprises an identifier of thedestination network and an identifier of the destination node within thedestination network.
 6. A method according to claim 2, wherein thedestination connection identifier comprises the destination nodeidentifier pre-pended or post-pended to the destination applicationlayer identifier.
 7. A method according to claim 2, wherein thedestination connection identifier comprises the destination applicationlayer identifier with the destination node identifier embedded therein.8. A method according to claim 2, wherein the destination nodeidentifier is based on a transport layer identifier for the destinationnode.
 9. A method according to claim 1, wherein the source nodeidentifier is unique within the telecommunications network.
 10. A methodaccording to claim 1, wherein the source node identifier is globallyunique.
 11. A method according to claim 1, wherein the source nodeidentifier comprises an identifier of at least a portion of the sourcenetwork and an identifier of the source node within the at least aportion of the source network.
 12. A method according to claim 1,wherein the source connection identifier comprises the source nodeidentifier pre-pended or post-pended to the source application layeridentifier.
 13. A method according to claim 1, wherein the sourceconnection identifier comprises the source application layer identifierwith the source node identifier embedded therein.
 14. A method accordingto claim 1, wherein the source node identifier is based on a transportlayer identifier for the source node.
 15. A non-transitorycomputer-readable storage medium comprising instructions for carryingout a method according to claim
 1. 16. A method according to claim 1,performed by a source node, wherein said source application layeridentifier is configured to identify user equipment associated with saidsource node.
 17. An apparatus comprising a source node comprising afirst base station for originating a connection to a destination nodecomprising a second base station of a cellular telecommunicationsnetwork, the source node comprising: a generator to generate a sourceapplication layer identifier, wherein said source application layeridentifier is configured to identify user equipment associated with saidsource node; a controller operable to retrieve a source node identifier;and a transmitter operable to transmit, from the source node comprisingthe first base station, the source application layer identifier and thesource node identifier to the destination node comprising the secondbase station to provide a source connection identifier for the requestedconnection between the source node and the destination node.
 18. Anapparatus according to claim 17 further comprising a receiver forreceiving a connection reply message, the reply message comprising adestination connection identifier, the destination connection identifiercomprising a destination application layer identifier for a connectionwithin the destination node and a destination node identifier.
 19. Anapparatus comprising a source node comprising a first base station fororiginating a connection to a destination node comprising a second basestation of a cellular telecommunications network, the source node beingoperable under program control to: generate a source application layeridentifier, wherein said source application layer identifier isconfigured to identify user equipment associated with said source code;retrieve a source node identifier; and transmit the source applicationlayer identifier and the source node identifier to the destination nodeto provide a source connection identifier for the requested connectionbetween the source node and the destination node.
 20. A method forestablishing a connection between a source node comprising a first basestation and a destination node comprising a second base station in acellular telecommunications network by transmitting a connection requestmessage, the message having a source application layer identifier forthe connection within the source node comprising the first base station,wherein said source application layer identifier is configured toidentify user equipment associated with said source node comprising saidfirst base station; and wherein the message further comprises a sourcenode identifier for the source node comprising said first base station.21. A system comprising a source node comprising a first base stationand a destination node comprising a second base station of a cellulartelecommunications network, said source node being operable to transmita connection request message, the message having a source applicationlayer identifier for the connection within the source node comprisingsaid first base station, wherein said source application layeridentifier is configured to identify user equipment associated with saidsource node comprising said first base station; and wherein the messagefurther comprises a source node identifier for the source node.